Rudy Giuliani‘s disgraced ex-police commissioner, Bernard Kerik, is back on the wrong side of the law – a federal grand jury slapped him with a new indictment yesterday.

Kerik, 52, was set to turn himself in to authorities this morning in preparation for an arraignment in White Plains federal court on charges that could land the longtime lawman in prison.

Magistrate Judge George Yanthis sealed the indictment pending Kerik’s court appearance, but sources familiar with the probe said the grand jury was presented with corruption and tax charges that included tax evasion, conspiracy and receiving unlawful gratuities.

The panel voted to indict New York City’s former top cop after meeting behind closed doors for approximately 3½ hours at the White Plains courthouse.

Kerik is expected to plead not guilty and has negotiated a package that would release him on $300,000 bail to be secured by his home in Franklin Lakes, N.J.

Defense attorney Kenneth Breen could not be reached for comment.

Kerik’s legal woes hounded Giuliani yesterday on the GOP presidential campaign trail in Iowa, where the former mayor admitted he goofed in making his pal police commissioner.

“I have pointed out that I think I made a mistake in not checking him out more carefully,” Giuliani said.

Among Kerik’s alleged crimes was a plot to secretly accept $160,000 in renovations to his Bronx apartment from a mob-linked construction firm while he was correction commissioner.

Kerik was also rapped for allegedly allowing a real-estate developer to pay $9,000 a month in rent on an Upper East Side luxury apartment where he lived with his family at around the time that he left the NYPD.

Neither of these allegedly unlawful gifts was declared as income.

Kerik enjoyed a decades-long rise from undercover cop, to correction commissioner, NYPD commissioner and 9/11 hero under Giuliani and interim minister of the interior in Iraq.

But his prospects took a dramatic downturn in December 2004 when President Bush nominated him to the top Homeland Security post, only to face the embarrassment of learning Kerik was hiding skeletons in his closet.

Kerik was forced to withdraw his name from consideration after it came to light he’d employed a nanny with immigration problems and failed to make proper tax filings.

Then came the revelations about two simultaneous extramarital affairs, with Judith Regan, the publisher of his memoir, and a city correction officer.

Within 18 months of the Homeland Security debacle, Kerik was facing prosecution by the Bronx DA’s Office.

Accused of improperly helping Interstate Industrial Corp. to do businesses with the city in exchange for the $160,000 in renovations and failing to inform city ethics regulators about a $28,000 loan from a real-estate developer, prison was a real possibility for Kerik.

He chose to cut his losses by pleading guilty to misdemeanor conflict-of-interest charges in June 2006 and was ordered him to pay $221,000 in fines and fees.